Electrochemical Reaction Mechanism Research Articles

A highly stable insertion type V1-xTixP solid solution as an anode material for high-rate lithium-ion batteries

As electric vehicles (EVs) grow in popularity, the demand for lithium-ion batteries (LIBs) simultaneously grows, and the fast-charging capability is becoming increasingly important. However, it is generally believed that graphite anode still suffers from a poor rate capability for fast-charging applications, and other insertion-type oxide anodes with a high rate capability exhibit too high Li+-ion insertion/extraction potential, which cannot meet a requirement for high energy density anodes. In this work, the hexagonal structure of V1-xTixP (x = 0.0, 0.25, and 1.0) phases were introduced as insertion-type anode materials for LIBs with a low reaction potential of Li+-ion insertion/extraction. The crystal structure and the corresponding electrochemical reaction mechanism of insertion-type anodes of TiP, VP, and MoP were compared. A facile strategy forming a substitutional solid solution is suggested to improve the electrochemical properties of anode materials by combining the end members among insertion-type VP, TiP, and MoP as forming V1-xTixP and V1-xMoxP compounds. V1-xTixP (x = 0.25) electrode, substituting V atoms with Ti atoms in VP structure, shows excellent long-term cycle stability at 1 A/g with a cycle retention of 87.7 % during 2500 cycles, delivering a two times higher capacity of 211.1 mAh g−1 compared to that of the commercial graphite electrode.

Electrochemical Behaviour and Sensing of Chlorpromazine at Polymer‐Free Kaolin‐Based Nanosodalite and Nanosodalite‐Graphene Foam Film modified Glassy Carbon Electrodes

AbstractA nanosodalite (SOD) was synthesized utilizing Cameroonian kaolin and then used to prepare a nanocomposite (SOD‐GF) with graphene foam (GF). The as‐synthesized materials were characterized using X‐ray diffractometry (XRD), Fourier transform‐infrared (FT‐IR) spectroscopy, N2 adsorption‐desorption and scanning electron microscopy coupled with emission dispersive X‐ray (SEM/EDX). The results show a pure sodalite with high degree of crystallinity with crystallite size and BET surface area of 38.3 nm and 22 m2/g, respectively. The composite's characterization revealed a well‐integrated material in which the structural integrity of each material is maintained, its surface area being 4‐fold that of pristine SOD. Stable SOD and SOD‐GF modified glassy carbon electrode (GCE) were prepared by drop coating without a binder and utilized to study the electrochemistry of chlorpromazine (CPZ) in acidic, neutral and basic pHs. It appeared that (i) CPZ's electrochemical oxidation was a two‐step one‐electron process at SOD/GCE and a one‐step two‐electron process at SOD‐GF/GCE and (ii) the electrochemical reaction mechanism was an EEC mechanism at SOD/GCE while at SOD‐GF/GCE the mechanism was EEC at pH<4 and EC for greater pH. SOD/GCE and SOD‐GF/GCE were used to sense CPZ within CPZ's concentration ranging from 0.5‐30 μM with low detection limits.

Preparation of a novel DNA-imprinted sensor based on chitosan and its highly sensitive detection of Pb2+

Lead ion is very harmful to the environment, so it is very important to study its detection methods. In this study, a novel electrochemical sensor was constructed by modifying deoxyribonucleic acid (DNA) on the electrode, which can be used for the detection of Pb2+ in the environment. Part of the mixed solution of chitosan (CS) and Pb2+ template ions was dropped onto the surface of a glassy carbon electrode. CS-Pb2+ film was cross-linked through sodium tripolyphosphate. And a novel DNA-imprinted sensor was prepared by electrodepositing CS-Pb2+ thin film with gold nanoparticles (AuNPs), removing Pb2+ templates, and immobilizing specific double-stranded DNA. The electroactive area, surface morphology, sensitivity, and electrochemical reaction mechanism of the DNA-imprinted sensor were analyzed. The elementary reaction steps were studied through electrochemical reaction kinetics analysis. The experimental results indicate that the DNA-imprinted electrochemical biosensor can quantitatively detect Pb2+ in the range of 10–100 μM (R2 = 0.9935), and its detection limit is 6.5074 μM (3σ/slope). The sensitivity of the electrochemical biosensor is 1.55233 × 10−6 A/μM, and its active areas is 6.233 cm2. The desorption mechanism and adsorption mechanism have been explored through dynamic parameter analysis. The novel DNA imprinted electrochemical biosensor developed in this paper provides a robust method for detecting lead ions in solution. Additionally, it establishes a solid groundwork for detecting other metal ions.

Regulating the Critical Intermediates of Dual-Atom Catalysts for CO2 Electroreduction.

Electrocatalysis is a very attractive way to achieve a sustainable carbon cycle by converting CO2 into organic fuels and feedstocks. Therefore, it is crucial to design advanced electrocatalysts by understanding the reaction mechanism of electrochemical CO2 reduction reaction (eCO2RR) with multiple electron transfers. Among electrocatalysts, dual-atom catalysts (DACs) are promising candidates due to their distinct electronic structures and extremely high atomic utilization efficiency. Herein, the eCO2RR mechanism and the identification of intermediates using advanced characterization techniques, with a particular focus on regulating the critical intermediates are systematically summarized. Further, the insightful understanding of the functionality of DACs originates from the variable metrics of electronic structures including orbital structure, charge distribution, and electron spin state, which influences the active sites and critical intermediates in eCO2RR processes. Based on the intrinsic relationship between variable metrics and critical intermediates, the optimized strategies of DACs are summarized containing the participation of synergistic atoms, engineering of the atomic coordination environment, regulation of the diversity of central metal atoms, and modulation of metal-support interaction. Finally, the challenges and future opportunities of atomically dispersed catalysts for eCO2RR processes are discussed.

Synthesis of Sb2Se3@PPy nanorod composite as cathode material for aluminum batteries

Aluminum batteries (ABs) are a promising alternative to lithium-ion batteries (LIBs) in the future. The development of aluminum batteries(ABs) is closely related to their cathode material. In this paper, we successfully designed and prepared a nanorod structure Sb2Se3@PPy as cathode material for ABs. It exhibits a high reversible capacity of 302 mAh/g at 0.2 A/g, and the capacity is maintained at about 210 mAh/g after 50 cycles. In addition, the electrochemical reaction mechanism and kinetic process of Sb2Se3@PPy were studied. The results showed that the PPy coating layer reduced the volume change of Sb2Se3, prevented irreversible deformation, enhanced the structural stability and electronic conductivity.

Study of the migration and distribution pathways of key corrosive species during high-temperature corrosion by means of atom probe tomography and δ35Cl isotope tracer

This study investigated the migration pathways and the dominant chlorine- and alkali-induced corrosion mechanisms of Ni-28Cr-13Al-0.6B-0.5 W alloy at 600ºC. The distribution of key elements (35Cl, 37Cl, Na, O, Ni, Cr, Al) at the alloy/oxide interface was analyzed by APT coupled with δ35Cl isotope labeling for tracing the competitiveness of organic chlorine and inorganic chlorine. The alloying element`s migration rate was in the order of Al > Cr > Ni > W. Cl diffused through oxide grain-boundaries as Cl- ions formed by the decomposition of sulfate-melt and corrosion in grain-boundaries was dominated by electrochemical reaction mechanisms. Na enhances the diffusion of elements by widening the grain-boundaries.

Electrochemical reaction mechanism of silicon nitride as negative electrode for all-solid-state Li-ion battery

Electrochemical reaction mechanism of silicon nitride as negative electrode for all-solid-state Li-ion battery

Distinguish MnO2/Mn2+ Conversion/ Zn2+ Intercalation/ H+ Conversion Chemistries at Different Potentials in Aqueous Zn||MnO2 Batteries

AbstractThe rechargeable aqueous Zn||MnO2 chemistry has been extensively explored, but its electrochemical reaction mechanisms, especially in the context of MnO2/Mn2+ conversion and Zn2+/H+ intercalation chemistry, remain not fully understood. Here, we designed an amphiphilic hydrogel electrolyte, which distinguished the MnO2/Mn2+ conversion, Zn2+ intercalation, and H+ intercalation and conversion processes at three distinct discharge plateaus of an aqueous Zn||MnO2 battery. The amphiphilic hydrogel electrolyte is featured with an extended electrochemical stability window up to 3.0 V, high ionic conductivity, Zn2+‐selective ion tunnels, and hydrophobic associations with cathode materials. This specifically designed electrolyte allows the MnO2/Mn2+ conversion reaction at a discharge plateau of 1.75 V. More interesting, the discharge plateaus of ~1.33 V, previously assigned as the co‐intercalation of Zn2+ and H+ ions in the MnO2 cathode, are specified as the exclusive intercalation of Zn2+ ions, leading to an ultra‐flat voltage plateau. Furthermore, with a distinct three‐step electrochemical energy storage process, a high areal capacity of 1.8 mAh cm−2 and high specific energy of 0.858 Wh cm−2, even at a low MnO2 loading mass of 0.5 mg cm−2 are achieved. To our knowledge, this is the first report to fully distinguish different mechanisms at different potentials in aqueous Zn||MnO2 batteries.

Distinguish MnO2/Mn2+ Conversion/ Zn2+ Intercalation/ H+ Conversion Chemistries at Different Potentials in Aqueous Zn||MnO2 Batteries.

The rechargeable aqueous Zn||MnO2 chemistry has been extensively explored, but its electrochemical reaction mechanisms, especially in the context of MnO2/Mn2+ conversion and Zn2+/H+ intercalation chemistry, remain not fully understood. Here, we designed an amphiphilic hydrogel electrolyte, which distinguished the MnO2/Mn2+ conversion, Zn2+ intercalation, and H+ intercalation and conversion processes at three distinct discharge plateaus of an aqueous Zn||MnO2 battery. The amphiphilic hydrogel electrolyte is featured with an extended electrochemical stability window up to 3.0 V, high ionic conductivity, Zn2+-selective ion tunnels, and hydrophobic associations with cathode materials. This specifically designed electrolyte allows the MnO2/Mn2+ conversion reaction at a discharge plateau of 1.75 V. More interesting, the discharge plateaus of ~1.33 V, previously assigned as the co-intercalation of Zn2+ and H+ ions in the MnO2 cathode, are specified as the exclusive intercalation of Zn2+ ions, leading to an ultra-flat voltage plateau. Furthermore, with a distinct three-step electrochemical energy storage process, a high areal capacity of 1.8 mAh cm-2 and high specific energy of 0.858 Wh cm-2, even at a low MnO2 loading mass of 0.5 mg cm-2 are achieved. To our knowledge, this is the first report to fully distinguish different mechanisms at different potentials in aqueous Zn||MnO2 batteries.

Unveiling the non-innocence of vanadium dopant in TiO2 nanocrystals for advanced energy storage and smart windows

Vanadium doped TiO2 NCs stand out as a promising candidate for energy storage applications due to its high electrical conductivity and redox properties. However, the thermodynamical behavior of the material under working conditions has not been explored and the reasons for its superior performance remain unlocked. This study explores the use of a combination of advanced in situ spectroscopy techniques, including x-ray absorption spectroscopy (XAS), spectro-electrochemistry (SEC), and electrochemical impedance spectroscopy (EIS) to provide unprecedented insights into the intricate electrochemical reaction mechanisms within these nanocrystals. Density functional theory calculations and EIS reveal the active role of substitutional V ions in the TiO2 anatase network as electron donors, enhancing surface charge and carrier density and improving pseudocapacitive properties. Cyclic voltammetry and in situ SEC reveal that V-doped TiO2 NCs exhibit significantly improved charge storage capacities, particularly in the pseudo-capacitance storage mechanism. In situ SEC and XAS analyses indicate that a more effective reduction of Ti4+ ions occurs during the electrochemical process in doped NCs, leading to higher charge capacitance and faster processes. Furthermore, in situ XAS measurements of the V K-edge revealed that the vanadium ions, beyond improving the redox behavior of the host, also actively participate in the reduction process. The significant changes in the V K-edge XANES and extended x-ray absorption fine structure spectra observed under reduction conditions can be ascribed to a change in the structure and oxidation state of the vanadium ions during the electrochemical reaction.

High-rate aqueous magnesium ion battery enabled by Li/Mg hybrid superconcentrated electrolyte

Rechargeable aqueous magnesium ion batteries (AMIBs) are considered a promising energy storage system due to the relatively high energy density, excellent rate performance and reversibility, and absence of dendrite formation during cycling. However, the high surface charge density of Mg2+ ions results in slow diffusion kinetics, and high voltage leads to excessive electrolyte decomposition at the electrode/aqueous electrolyte interface, thereby limiting the development of high-energy–density MIBs. In this work, we extend the electrochemical stability window of the aqueous electrolyte to 2.1 V by using a hybrid ion superconcentrated electrolyte at concentrations not achievable with Mg2+ electrolytes alone. The AMIB with a water-in-salt (WIS) electrolyte delivers discharge capacities of up to 200.6 and 84.4 mAh g−1, and energy densities of 170.1 and 68.1 Wh Kg−1 at 0.5 and 20 A g−1, respectively, representing excellent rate performance, while retaining 85 % of the specific capacity after 2000 cycles. Additionally, we explore the corresponding electrochemical reaction mechanism, revealing the synergistic effect of Mg2+ and Li+ ions in the charge/discharge process, which supports the excellent electrochemical performance of AMIB.

Unraveling high efficiency multi-step sodium storage and bidirectional redox kinetics synergy mechanism of cobalt-doping vanadium disulfide anode

Sodium-based storage devices based on conversion-type metal sulfide anodes have attracted great attention due to their multivalent ion redox reaction ability. However, they also suffer from sodium polysulfides (NaPSs) shuttling problems during the sluggish Na+ redox process, leading to “voltage failure” and rapid capacity decay. Herein, a metal cobalt-doping vanadium disulfide (Co-VS2) is proposed to simultaneously accelerate the electrochemical reaction of VS2 and enhance the bidirectional redox of soluble NaPSs. It is found that the strong adsorption of NaPSs by V-Co alloy nanoparticles formed in situ during the conversion reaction of Co-VS2 can effectively inhibit the dissolution and shuttle of NaPSs, and thermodynamically reduce the formation energy barrier of the reaction path to effectively drive the complete conversion reaction, while the metal transition of Co elements enhances reconversion kinetics to achieve high reversibility. Moreover, Co-VS2 also produce abundant sulfur vacancies and unsaturated sulfur edge defects, significantly improve ionic/electron diffusion kinetics. Therefore, the Co-VS2 anode exhibits ultrahigh rate capability (562 mA h g−1 at 5 A g−1), high initial coulombic efficiency (≈90%) and 12,000 ultralong cycle life with capacity retention of 90% in sodium-ion batteries (SIBs), as well as impressive energy/power density (118 Wh kg−1/31,250 W kg−1) and over 10,000 stable cycles in sodium-ion hybrid capacitors (SIHCs). Moreover, the pouch cell-type SIHC displays a high-energy density of 102 Wh kg−1 and exceed 600 stable cycles. This work deepens the understanding of the electrochemical reaction mechanism of conversion-type metal sulfide anodes and provides a valuable solution to the shuttling of NaPSs in SIBs and SIHCs.

Development of a Potential-Modulated Electrochemiluminescence Measurement System for Selective and Sensitive Determination of the Controlled Drug Codeine.

Codeine is a common analgesic drug that is a pro-drug of morphine. It also has a high risk of abuse as a recreational drug because of its extensive distribution as an OTC drug. Therefore, sensitive and selective screening methods for codeine are crucial in forensic analytical chemistry. To date, a commercial analytical kit has not been developed for dedicated codeine determination, and there is a need for an analytical method to quantify codeine in the field. In the present work, potential modulation was combined with electrochemiluminescence (ECL) for sensitive determination of codeine. The potential modulated technique involved applying a signal to electrodes by superimposing an AC potential on the DC potential. When tris(2,2'-bipyridine)ruthenium(II) ([Ru(bpy)3]2+) was used as an ECL emitter, ECL activity was confirmed for codeine. A detailed investigation of the electrochemical reaction mechanism suggested a characteristic ECL reaction mechanism involving electrochemical oxidation of the opioid framework. Besides the usual ECL reaction derived from the amine framework, selective detection of codeine was possible under the measurement conditions, with clear luminescence observed in an acidic solution. The sensitivity of codeine detection by potential modulated-ECL was one order of magnitude higher than that obtained with the conventional potential sweep method. The proposed method was applied to codeine determination in actual prescription medications and OTC drug samples. Codeine was selectively determined from other compounds in medications and showed good linearity with a low detection limit (150 ng mL-1).

Study on the electrochemical reaction mechanism of non-corrosive and long-life rechargeable aluminum battery

Study on the electrochemical reaction mechanism of non-corrosive and long-life rechargeable aluminum battery

Recent Advances of Flexible MXene and its Composites for Supercapacitors.

MXenes have unique properties such as high electrical conductivity, excellent mechanical properties, rich surface chemistry, and convenient processability. These characteristics make them ideal for producing flexible materials with tunable microstructures. This paper reviews the laboratory research progress of flexible MXene and its composite materials for supercapacitors. And introduces the general synthesis method of MXene, as well as the preparation and properties of flexible MXene. By analyzing the current research status, the electrochemical reaction mechanism of MXene was explained from the perspectives of electrolyte and surface terminating groups. This review particularly emphasizes the composite methods of freestanding flexible MXene composite materials. The review points out that the biggest problem with flexible MXene electrodes is severe self-stacking, which reduces the number of chemically active sites, weakens ion accessibility, and ultimately lowers electrochemical performance. Therefore, it is necessary to composite MXene with other electrode materials and design a good microstructure. This review affirms the enormous potential of flexible MXene and its composite materials in the field of supercapacitors. In addition, the challenges and possible improvements faced by MXene based materials in practical applications were also discussed.

Stable 2,5‐Dihydroxy‐1,4‐benzoquinone Based Organic Cathode Enabled by Coordination Polymer Formation and Binder Optimization

AbstractOrganic electrode materials are gaining increased attention in energy storage applications, but often encounter challenges such as low capacity and poor cycling stability. This paper explores the utilization of a 1‐D coordination polymer, copper(II)‐2,5‐dihydroxy‐1,4‐benzoquinone (Cu‐DHBQ), as a cathode material for Li‐ion batteries for the first time. Cu‐DHBQ is air‐stable, devoid of coordinated water molecules, and possesses a high theoretical capacity of 266 mAh g−1. With an optimal sodium alginate (SA) binder content of 25 wt%, the Cu‐DHBQ cathode demonstrates a notable initial capacity of 214 mAh g−1 and outstanding cycling stability, retaining 210 mAh g−1 (98% capacity retention) after 200 cycles at a current rate of 100 mA g−1. A comprehensive investigation into the capacity fading mechanisms, the bonding capability of the SA binder, and the interactions between Cu‐DHBQ and SA is conducted using scanning electron microscope (SEM), peel tests, and Fourier transform infrared spectroscopy (FTIR), respectively. Additionally, the electrochemical reaction mechanisms of Cu‐DHBQ are examined using ex situ X‐ray photoelectron spectroscopy (XPS) and FTIR. These findings offer valuable insights into understanding the electrochemical properties of coordination polymers and metal‐organic frameworks based on DHBQ, shedding light on their potential as materials for battery electrodes.

Electrochemical reaction mechanism of milled surface of NiTi shape memory alloy

NiTi shape memory alloy is widely used in medical field because of its excellent properties. Milling machining has become one of the main processing methods in the medical field due to its good shape adaptability. However, the change of the shape and properties of milled surface affects its biocompatibility and corrosion resistance. Electrochemical machining is used as the follow-up process of milling machining. The polarization curve method, cyclic voltammetry method and constant potential electrolysis are used in this paper to study the electrochemical reaction mechanism of the NiTi alloy milled surface. The results show that the plastic deformation layer appears compared with the original material, making electrode reactions and electron transfer relatively difficult. The surface eventually forms TiO2, without the formation of Ni-related oxide. The electrochemical reaction mechanism of the NiTi alloy milled surface in the HClO4-CH3COOH system provide important theoretical guidance for the production and manufacturing of medical products.

Advanced Polymers in Cathodes and Electrolytes for Lithium-Sulfur Batteries: Progress and Prospects.

Lithium-sulfur (Li-S) batteries, which store energy through reversible redox reactions with multiple electron transfers, are seen as one of the promising energy storage systems of the future due to their outstanding advantages. However, the shuttle effect, volume expansion, low conductivity of sulfur cathodes, and uncontrollable dendrite phenomenon of the lithium anodes have hindered the further application of Li-S batteries. In order to solve the problems and clarify the electrochemical reaction mechanism, various types of materials, such as metal compounds and carbon materials, are used in Li-S batteries. Polymers, as a class of inexpensive, lightweight, and electrochemically stable materials, enable the construction of low-cost, high-specific capacity Li-S batteries. Moreover, polymers can be multifunctionalized by obtaining rich structures through molecular design, allowing them to be applied not only in cathodes, but also in binders and solid-state electrolytes to optimize electrochemical performance from multiple perspectives. The most widely used areas related to polymer applications in Li-S batteries, including cathodes and electrolytes, are selected for a comprehensive overview, and the relevant mechanisms of polymer action in different components are discussed. Finally, the prospects for the practical application of polymers in Li-S batteries are presented in terms of advanced characterization and mechanistic analysis.

Niobium-Based Oxide for Anode Materials for Lithium-Ion Batteries.

Recently, it has become imperative to develop high energy density as well as high safety lithium-ion batteries (LIBS) to meet the growing energy demand. Among the anode materials used in LIBs, the currently used commercial graphite has low capacity and is a safety hazard due to the formation of lithium dendrites during the reaction. Among the transition metal oxide (TMO) anode materials, TMO based on the intercalation reaction mechanism has a more stable structure and is less prone to volume expansion than TMO based on the conversion reaction mechanism, especially the niobium-based oxide in it has attracted much attention. Niobium-based oxides have a high operating potential to inhibit the formation of lithium dendrites and lithium deposits to ensure safety, and have stable and fast lithium ion transport channels with excellent multiplicative performance. This review summarizes the recent developments of niobium-based oxides as anode materials for lithium-ion batteries, discusses the special structure and electrochemical reaction mechanism of the materials, the synthesis methods and morphology of nanostructures, deficiencies and improvement strategies, and looks into the future developments and challenges of niobium-based oxide anode materials.

Ultrasensitive Plasmon-Enhanced Infrared Spectroelectrochemistry.

IR spectroelectrochemistry (EC-IR) is a cutting-edge operando method for exploring electrochemical reaction mechanisms. However, detection of interfacial molecules is challenged by the limited sensitivity of existing EC-IR platforms due to the lack of high-enhancement substrates. Here, we propose an innovative plasmon-enhanced infrared spectroelectrochemistry (EC-PEIRS) platform to overcome this sensitivity limitation. Plasmonic antennae with ultrahigh IR signal enhancement are electrically connected via monolayer graphene while preserving optical path integrity, serving as both the electrode and IR substrate. The [Fe(CN)6 ]3- /[Fe(CN)6 ]4- redox reaction and electrochemical CO2 reduction reaction (CO2 RR) are investigated on the EC-PEIRS platform with a remarkable signal enhancement. Notably, the enhanced IR signals enable a reconstruction of the electrochemical curve of the redox reactions and unveil the CO2 RR mechanism. This study presents a promising technique for boosting the in-depth understanding of interfacial events across diverse applications.